Community Challenge: SD-WAN, Explained

SD-WAN is a popular topic these days, but it can be difficult to explain to a layperson.

Your challenge this month is to describe SD-WAN in non-technical terms.

Imagine you had to explain the concept to a classroom of smart but non-technical high school students, or to an acquaintance at a cocktail party (clearly a raging party!). What's a real-world analogy you can use to describe what SD-WAN is and how it works?

We encourage you to use pictures or diagrams (or even video!?) to help your explanation come to life.

The winners will each receive a Meraki mini-fridge (picture below)!

How to enter

Submit your contest entry in a comment on this blog post before 11 a.m. PDT on Monday (December 10, 2018). This time around, entries won’t be made public until voting starts. After you submit your entry, you’ll see a message reading “Your post will appear as soon as it is approved.”

The Community Favorite — chosen by you, our Community members. Cast your vote by giving kudos () to your favorite entries. The entry with the most kudos from community members who aren't Meraki employees will win!

The Meraki Favorite — a panel of experts here at Meraki will select the Meraki Favorite prize, judging entries on creativity, completeness, and accuracy.

SD-WAN is a way to remove high cost, low speed connections from your locations and replace them with lower cost, higher speed connections. SD-WAN gives you flexibility of choosing any provider that can give you public internet connection and create a secure connection on it. Save money and get more for it, what else can you ask for.

SD-WAN is similar to google maps, or waze GPS app. The app builds a route, and uses the traffic volume, transit time, and alternate paths, to find the best route to the destination. But like these apps, you can also enter additional criteria such as avoid tolls, avoid bad roads, avoid this and that, etc... there is even the option to take the best route based on the transit type, such as walking, or driving, or bike riding. SD-WAN functions similarly. You can simply take the best path, but when traffic picks up, select and alternative route. Or if using one application called bike, then take the path selected for bike. If using an application called bus, then take the path defined for bus. if using an application called car, avoid delays SD-WAN is basically a super fast way to calculate traffic and provide the best path based on the application, or method of transport, and the costs associated with that selection.

Remember the olden days, when every house had a land line? If you wanted to talk to your relatives, you picked up the phone and dialed via your land line. In fact, it never crossed your mind to use anything but your land line - why would it?

Fast forward a few years, and cell phones are pervasive. Thorough testing has shown that the call quality isn't quite as good as a land line, yet call quality is rarely an issue. Besides, the best-of-breed phones can handle two SIM cards. If you can't get a Verizon signal, the phone will automatically switch to AT&T's network.

The world of network connectivity is going through the same kind of generational change right now. Instead of MPLS circuits, which everyone used to buy without thinking twice about it, companies are now buying Internet bandwidth because it's so cheap. And with a Meraki MX, if one Internet circuit is suffering, the other one will automatically be used instead.

SD-WAN, put simply, is the ability to make your network redundant. In a business world it can be crucial that you have a working internet connection for both corporate computers, and in some cases point of sale. With SD-WAN you are able to take multiple internet connections, referred to as uplinks and have them act in tandem to strengthen your network. You can have one be active, and the other sitting there waiting for the main one to fail due to an outage, so it can then take its place as the new active connection. Alternatively, they can both be active and you can shape the traffic as you see fit.

Shaping traffic is a whole different can of worms, but to briefly touch on it, you can balance the load of your traffic between your two uplinks and even go so far as to set custom rules that only certain traffic traverse one uplink and other traffic out another. In a real world scenario, you may want to allow video or streaming traffic out your faster internet uplink, and other traffic like web browsing out of a slower uplink.

You could even set rules for traffic based on a specific computer being able to only access one of the uplinks, or a specific department in an office building, the power and choice is all yours.

SD-WAN is a faster and lower cost way to build (and manage) long distance networks. Instead of individual (typically command line based) control of, for instance, routers, control is centralized under one interface. This has multiple advantages: It simplifies network policy configuration and deployment, which allows changes across an organization through one central interface instead of making individual changes per branch/location/device. Also, it allows multiple paths to be utilized, such as broadband connections, instead of having to use expensive private circuits such as MPLS, point-to-point, etc. These benefits combine to lower costs -- both in IT staff resources and in infrastructure fees. The result is a cheaper, more agile, easier to manage network.

I was asked this question the other day, and the answer came as quick as it was asked.

My answer was, SD-WAN is kind of like Waze, the app for directions.

Say your driving along, and you have plans to get someplace important. Along the way, a bridge is out, or a road is closed. No worries, Waze (SD-WAN) simply picks another road. The beauty part is, you get to choose those other roads, and they can be as quick and reliable as you want. Or...cheap and plenty as needed. It works for congestion too...or to mitigate it. Simply tell Waze (SD-WAN) that you don't want to pay tolls or go on highways...no problem. Do you have passengers who want to see scenic routes...no problem (this might be similar to telling applications to go over a more secure route).

A popular buzzword in the IT community has been, and continues to be 'SD-WAN'. Software-Defined WAN refers to the ability to use software to make decisions when it comes to routing traffic between sites within a corporation or business. This is different from the legacy WAN (wide area network) architecture, which traditionally utilized a primary path, and sometimes a secondary or failover path. This legacy model introduced issues related to paying for a secondary connection (usually broadband or other low-cost internet) that may never be used, or may only be used a few days a year. A big problem with this was the inability for IT teams to determine if the secondary path was working as expected without testing in a DR scenario; ISP changes or configuration adjustments could result in this back-up tunnel not performing as expected, if at all. With SD-WAN, you're able to utilize multiple connections to connect remote sites to your primary Data Center simultaneously, allowing for better performance, and better redundancy to your remote sites (in essence, allowing a business to utilize multiple connections they already pay for without needing a fail scenario to leverage them). The benefit to this offering is that a business can configure their SD-WAN devices so there is a preferred route for critical traffic, and then define parameters on the links so that if one is not performing well, there is an automatic change in the routes the traffic takes, making an SD-WAN architecture highly-available and automated. At the end of the day, there 'can' be cost savings, but what I see mostly is that for the same spend, a business can greatly improve the performance and reliability of their WAN offering.

SD-WAN - Think it like an secure and private railroad into a public landscape, there your tracks and switches will be your network and end stations will be your headquarters and branches. Every track and switches connects automatic to your private network.

Software-defined networking (SDN) is a design or construct with a purpose to make networks more responsive and flexible. The goal is to improve network control by enabling engineers to respond quickly to changing business requirement through centralized control.

Like SDN, SD-WAN is the shortening for software-defined networking in a wide area network (WAN). An SD-WAN simplifies the management and operation of a WAN through centralized control or by separating the networking hardware from its control mechanism.

SD-WAN allows a person / company the ability to create network redundancy between their data center and their sites / locations using low cost bandwidth such as broadband. Network redundancy can be very costly and complex the conventional way while SD-WAN simplifies the experience and allow you to scale eaisily when using Meraki MX devices.

SD-WAN, or Software-Defined Wide-Area Networking, is a subset of Software-Defined Networking (SDN), which is itself an umbrella term encompassing several network technologies with the purpose of making the network agile and flexible. SDN includes the common network boundaries, or delineations, such as:

SDA - Software-Defined Access works commonly in the campus network delineation such as wired and wireless access for endpoints

SDWAN - Software-Defined Wide-Area Network focuses primarily on WAN technologies which includes public access circuits such as Direct Internet or MPLS

Each of these delineations share the same four basic pillars, or goals:

Abstraction - De-coupling the Management plane, the Control plane and the Data plane allows for simplified management in the User Interface while allowing for configurations to be executed but the complexity is hidden from human eyes.

SD-WAN incorporates the use of "overlays" to accomplish these goals. The idea is to create a multi-path OSI Layer 3 network as the "underlay", or foundation. The underlay should be highly available and resilient, able to re-route in case of any path outage. Overlay technologies such as DMVPN and mGRe are used to create an OSI Layer 2 tunnel from end-to-end. As this statement implies, end devices are able to communicate with other end devices at Layer 2, ensuring that the complexity of the underlay is completely transparent. To manage such an architecture manually would be a very large undertaking because first of all one must manage the complexity of the underlay, then one must manage the overlay as an entirely separate network. This is the advantage of Abstraction and Automation. A centralized management platform is able to communicate directly to network appliances over the Management plane, while network devices can communicate with each other using the Control plane. Separating these planes out of the traditional single-use Data plane ensures that things like configurations, path selections and policy enforcement can happen unimpeded by events which may occur on the Data plane.

Below is a high-level example of a typical use-case topology for SD-WAN:

there are multiple paths you could take motorways (MPLS), country lanes (Internet) or you could even fly (LTE).

using SD-WAN is always letting you know the best way to go at all times

sometimes the motorway is busy or an accident slows down traffic so you may be better off on the country lane

maybe there is no other choice but to fly as its the faster/only option

SD-WAN manages and monitors all available routes and provides traffic with the best path to take

SD-WAN also provides options:

maybe you want to split your traffic sending all your traffic send your important traffic down the motorways and your bulk traffic down the country lanes so that you know the motorway is always running at its top speed

if some of the bulk traffic slows down on the country lanes its not so bad as you critical traffic is running fine on the motorway

SD-WAN provides options to use multiple WAN technologies to provide additional bandwidth and resilience with cost savings to go with it

Imagine you are a rich person living in a beautiful private island, right across a town on the mainland, where your office is located. Your island is connected to the mainland by a bridge, so you can commute to work by car, boat or if you are really in a rush, you can take your helicopter (remember I told you are rich!). No matter what happens, you really need to commute to the office. Most of the time you can just commute by car, no problem. If the traffic is bad, and you are not in a rush, you can commute on your boat. But if the traffic is bad and you are really in a rush, you can commute on your helicopter! (pretty awesome eh!)

Now imagine:

You = Data

Car = Internet Fibre Link

Boat = Internet Cable Link

Helicopter = Wireless 4G Link

SD-WAN is the magic that allows your data to reach its destination using the best available path without complex network setups

SDWAN is comparable to a shopping centre at a location which has many roads leading to it. Some of these roads are sealed, some are dirt. Generally speaking, the sealed roads provide a quicker path to and from the shopping centre. In order to best distribute traffic, the 4 wheel drive vehicles leave the shopping centre via the dirt road and the normal vehicles leave the shopping centre via the sealed road (scenic path). Whilst the luxury cars leave the shopping centre via the more direct sealed road.

However, on rare occasions during bad weather some of the roads become flooded which greatly reduces or completely cut off access. When such events occur an alternate path is chosen.

For example, if the luxury cars are able to but greatly impacted or totally unable to go via the most direct sealed road due to flooding, they will try the scenic route sealed road followed by the dirt road until a more reliable path is viable. Each luxury vehicle will check the status of the roads as they leave the shopping centre. Alternatively if the dirt road and sealed scenic road is flooded, the 4 wheel drive vehicle will go via the direct sealed road, again each 4 wheel drive will check the status of the roads before they leave the shopping centre.

Before jumping in to understand SDWAN, we need to understand what is a WAN. The acronym stands for Wide Area Network which basically means your big cloud which connects all your offices together so they can talk to each other. If you only have two offices, for example, you can imagine it like a pipe connecting your two offices together. Usually this WAN service is paid service just like how you get your Internet services.

With SDWAN which stands for Software Defined WAN is like a smart WAN, if I could say that. It is a technology that is capable of using any Internet services (DSL, fibre, 4G, etc) to provide you similar result what WAN was offering. So you could use for example, one Internet using fibre service and the other using DSL.

However, its not only that. You can use different combination of these Internet services together to provide more resiliency to the WAN connection. By resiliency, we mean, your WAN connection will be more powerful and less prone to connection problems simply because it will not be relying on just one service.Just using the last example, if your Fibre Internet had issues, you still have connection to your other offices via the DSL Internet.

With having this option of using different services concurrently, you can also control your traffic flow how it traverses from one office to other. For eg you may want business critical traffic over fibre so it is fast and less important traffic over DSL.

Finally, the best part is, you can have the combination using existing WAN services as well. For eg, Fibre Internet and your existing WAN. Usually this is the recommended practice as most of the times a customer will typically have a dedicated WAN service already in place; he can simply add an Internet service and use SDWAN over them.

For SDWAN between all your offices, you will need to ensure all the offices have SDWAN compliant devices to support this technology.

A Digital Network normally software driven with open APi's instantiated on flexible and capable hardware to express business intent and align network behavior to business objectives. With the following key capability; secure, policy driven, automated, flexible and scalable.

Imagine you want to drive with a group of 20 person from Oslo to Madrid. You have 3 different typ of cars.

1 four wheel drive Car. (5 person but not as safe)

1 Limousine (8 persons very safe car)

1 Ferrari (2 Person fast but not as safe)

Now there are a lot of different roads you can take but all have different challenge.

The Highway (often jammed)

The Road true the Mountains (Off-road but alway free of traffic)

The Small Roads true all the City's and village (the longest way)

Now, you need to bring all Person as fast as Possible and as Safe as Possible from Oslo to Madrid.

That's the moment you will use SD-WAN. It will measure the state of the road and how much traffic jam you have on all Roads, based on this it will select the best Car and how fast you will get from Oslo to Madrid.

As you can not take all person at once, SD-WAN will calculate witch will be the best Road, Car to go back to Oslo and get the rest of the Person.

I hope you just got a felling what SD-WAN is doing when you have more that one WAN connection and you want to Secure transport as much data at a time.

Imagine SD-WAN like a traffic police officer standing in the middle of a busy crossroad, and network frames as road vehicles.

His primary task is to regulate traffic so that everyone gets to his work as soon as possible. The SD-WAN will forward frames to the right path according to their destination.

However he must give priority to emergency services. Likewise SD-WAN will treat delay sensitive frames like voice and video, where loss matters, with high priority and guide them to an unblocked way.

Of course the officer has with him a police radio, in order to receive instructions from the traffic control and decide better where to divert the traffic. Likewise in SD-WAN the routing decisions are controlled by the admins centrally and instructions are pushed to each individual wan router.

First, let’s see what WAN is. Compared to LAN, which is Local Area Network, WAN is a world-wide interconnection of these smaller networks, hence called: Wide Area Network. LAN is more like driving a car and LAN is similar to flying by plane. Keeping the same example, flying a plane is so complex that is has to be at least partially automated: it follows a radio beacon to fly to the right direction, also a computer helps navigation and controls the plane. Furthermore, traffic is managed from centralized places: flight control towers. Similarly, SD (Software Defined) - WAN, by heavily relying on software, helps to automate routine tasks on a large scale: when a complex and versatile large set of network devices have to be configured behind a global network. This helps reduce number of errors and costs as well, and provides greater agility, especially because of the centrally managed nature. Similarly to a flight control tower it will oversee, control or limit traffic to certain areas. It is pretty much like aviation, but instead of carrying real payload, information is carried through the existing global network mediums, but with a better management which is easier to sustain and maintain.

These days people want to access information any time any where from any device. Mobile devices and cloud computing make it possible but it causes management complexity, application performance unpredictability, and data vulnerability.

There are two primary network :

LAN : - LAN connected devices insight of office together.

WAN: - WAN is connected your office to other side to around the world. Without WAN its like not having the Internet access.

SD-WAN is a software-defined approach to managing the wide-area network, or WAN Which makes IT works Smarter , Faster and Lower cost.

Let’s understand how SD-WAN works:

10s,100s or 1000s WAN routers are communicating to each other over long distances. With each routers having Data Plane and Control plane. Data plane is holds the information that is being sent or received Data. Control plane determines where that data should go. However someone need to program Control plane with the rule and how to handle network traffic on dataplane.

Let’s take Business case with example of large retail store chain:

A large Retail store chain with 1000 stores needs to deploy video application across the branches. Lets assume each store having one router that need 10 commands to implement correct configuration for new Video application. Assuming customer running 1000 branches and he wants to implement video application policy for all branches without any error.

If each command takes 6 sec to implement that means one branch required 1 min to implement new policy. It means 1* 1000= 1000 Min required to implement new policy.

If we are doing this manually then it complex, error prom and take long time. if any mistake happen with one of those command will do hunting and troubleshooting for the same that will impact IT resources. it may paralyze the businesses.

This problem can be overcome by developing programming tools and script. Here SDWAN introduced to do all automation on WAN devices. In SDWAN all control plane is centralize so its easy to manage and easy deploy new policy simultaneously. In SD-WAN we can define all business critical app on MPLS network and social media app on low priority. If any new policy implement it will automatically distributed and implemented across organization in second.

The modern workforce is increasingly mobile, and business-critical applications are running over the Internet across multiple clouds. SD-WAN Technology automatically determine the most effective way to route traffic to and from branch offices and data center sites. SD-WAN always choose best path to route traffic irrespective of transport carrier e.g. MPLS, 3G/4G LTE etc.

With the help of SD-WAN Technology Network administrators can use bandwidth more efficiently and can help ensure the highest level of performance for critical applications without sacrificing security or data privacy.

These days people expect access to information anytime, anywhere & from any device. Cloud computing & mobile devices have helped to make this possible but, the networks that keep everything connected keep growing & are becoming more & more complicated, especially to manage.

There are two types of primary networks, a local area network (LAN for short) & a wide area network called a WAN.

A LAN network connects all the devices inside your office together while the WANs connect your office to other offices & remote sites that could be anywhere in the world. A new technology is being adopted by many companies currently called SD-WAN which is the next generation of WANs.

The SD in SD-WAN stands for Software Defined which uses software to make the configuration of WANs work smarter, Faster & at a lower cost. Essentially, SD-WAN is a better way to build & manage long distance networks.

Why? How does it work?

A traditional WAN is made of tens, hundreds or even thousands of routers that talk to each other over long distances.

Within each router there is a data plane & a control plane. The data plane contains the data being sent or received while the control plane controls where that data should go.

The control plane of each router needs to be programed by someone with a set of rules that govern how to handle the traffic from the data plane. This is usually done by entering a set of commands into a command line interface known as a CLI by a network administrator which can be a manual, time consuming & an error prone process.

Take a large retail store chain with 500+ branches around the world that needs to deploy a new application. Each location may have a router on site that needs 10 commands entered for the correct handling of the video application. Thats 10 commands x 500 sites which is 5000 commands. If each command takes 30 seconds to configure, that adds up to over 41 hours, not to mention the planning time for each site.

This is a very cumbersome & error prone process, imagine making a mistake in one of those commands & having to hunt down root cause of the error or troubleshoot the application. Personnel & IT resources would be severely impacted.

With SD-WAN this whole process is greatly simplified. For starters, parts of the control plane are centralised, that way changes to the control plane can be grouped, simultaneously & easily managed across the entire WAN using business defined rules & most importantly from a central management tool.

This added simplicity makes it easy to take advantage of broadband internet connections instead of relying on expensive private circuits. Business critical applications can be given a secure & higher priority link between locations that is controlled & defined within the central management tool while other applications that might be taking productivity away from employees like social media can be given a lower priority or even blocked altogether with a rule again deployed from the central management tool to all sites in seconds.

You can compare SD-WAN to Waze (the popular GPS software) but for IP packets. You want to send the IP packets (the cars of the internet) the optimal way. Multiple factors determine that optimal way.

You should continuously keep an eye on how busy the roads (your uplinks) are and update your decisions based on those findings.

You should also make sure that packets take the optimal route for their "specific" application. Just like Waze gives regular cars the optimal route for cars, and trucks the optimal route for trucks, SD-WAN can send voice traffic which has very particular needs a predefined way...

If you have an expensive line you want to leverage this line, a bit like setting up toll passes in Waze to leverage toll roads you have access to.

If an uplink breaks down you navigate around it, just like Waze does during road works and accidents.

Where all this used to be impossible/hard/require extensive provider involvement (read: expensive lines) SD-WAN solutions allow to leverage cheaper internet lines and use them as optimally as possible. All the while keeping configuration and day to day management easy and intuitive.

SD-WAN can be described in simple terms as having 10 cars driving on a highway, each different color, but only Red, and Blue cars have the highest priority to go first ahead of other cars. The rest have to wait until road is clear for them to pass.

Think in your traffic and navigation app that analyzes real-time traffic and road info, giving you a opportunity to save time and gas money.This is SD-WAN. The Meraki´s technology determines which is the better link to your information and use this to improve security, economy and fastest delivery.

SD-WAN is like smartphone GPS for your network. Old networks still pass traffic like travelers in the Wild West, going from town to town (hops), asking for directions to their destination. Maps made it easier to find a place or route that you or someone else had already been to, but reading a map and figuring out the path at 80 MPH slows you down. SD-WAN takes all the great capabilities of your automated GPS, like warning you if the path you're are on will slow you down due to traffic, re-route you around an accident, or allow you to set preferences like avoiding tolls; and puts them into your network so you traffic becomes smarter and avoids latency, paths that are overloaded or broken, or preferences like sending kitten videos over a cheap circuit. This allows you to make your network smarter, more efficient, and able to correct issues before they potentially become larger problems.

SD-WAN is like when you're taking the school bus to school in the morning, the bus is equipped with Waze where it will always try to get you to school the quickest, most efficient way. For example, Monday it can take Washington St like it does usually. But on Wednesday due to some unforeseen heavy traffic, bus took Main St instead. It got to school slightly slower than usual but quicker than it would if it took congested Washington St.

Also since it's your school bus trying to get you to school, it'll always try to get you there safely.

There's SD-WAN in a nutshell, network connectivity in a secure, efficient, automated fashion.

It's basically fancy WAZE for network connectivity.. However, instead of just the route to your destination possibly changing, the vehicle you use to reach your destination may change. Additionally, we can write rules for Dave, so that he always has to take the stinky Yugo anywhere he goes... because no one likes Dave. But we all like Karl and our business really needs Karl, so we will write a rule to always give Karl the best vehicle we have. And, if anything ever happens and Karl's vehicle isn't available, he immediately gets to share Dave's stinky Yugo. For better or worse... And, also like Waze, SD-WAN can make life a bit more efficient and, at times, easier.

The SD-WAN solution is like our cardiovascular system, of course working in a simpler way.

We consider that the Human Body is the company, the Heart is the Headquarter , the system of veins and arteries is the internet links, the organs are the branches and the brain is the cloud.

The image below represents well:

The company - The Human Body

Now the explanation of each of them:

The Heart = The Headquarter

The headquarter

The Heart is the main part of the system that pumps blood through the veins and arteries, it is the Headquarter of a company, there are all the important parts of the company and it needs to have communication with all the other parts of the human body / company.

The Blood = Data for transportation

The Blood that is the material to be transported with all the necessary content for the vital functioning of all parts of the body, is the data transported between Headquarter / Branch and Cloud.

The Veins and Arteries = Internet Links and MPLS

blood in the vein / artery - the data passing through the link

The veins and arteries that have the role of carrying the blood to the various parts of the body are the internet links that carry and bring the information necessary for the operation of the whole company without this communication the company / human body does not survive.

The organs = The branchesThe organs - the branches

The organs, which have important functions in the human body, each in its particular function, but which all work together with the heart are the company branches.

The Brain = The Cloud

The brain - the cloud

The Brain that has all the control and orchestration of the whole organism and the control of the human body is the Cloud, where it has several applications and a series of information essential for the operation of the company, in it is also the management system of Meraki one can not be without communication with the brain (although Meraki works without this communication)

How its work?

The heart without communication with the organs

On the whole system: the Heart (Headquarter) must have communication at all times with the Brain (Cloud) and with the organs (branches), correct? one depends on the other in this system. Imagine if we had just a vein / arteries being used to carry blood between these points and it failed? What would happen? Some of the organs would begin to fail, and consequently would lead to a breakdown in the entire organism that could lead to death. The same thing would happen to the company without a subsidiary, we need a way for this system cannot fail.

The SD-WAN System - The redundancies

The redundant way

Now, our "SD-WAN" that solves this problem, it guarantees that the heart and the organs receive the blood with the redundancy of the veins / arteries (internet links) and maintain the communication with the Cloud, and in case some path fails , all the blood is directed to the other. In addition we have a third redundancy and the option to choose the shortest route to reach the destination, being chosen intelligently by our system. This is how the Meraki SD-WAN works.

SD-WAN stands for Software-Defined Wide Area Network. Traditionally, networks were defined by the hardware devices and the circuits connecting them. SD-WANs are defined by software that is downloaded into devices that control the movement of data packets. One hardware network can support multiple esparate software-defined networks. This is similar to a VLAN (Virtual Local Area Network) where one Ethernet switch supports two separate Ethernet LANs. Because of the high cost of wide area circuits, the benefits from SD-WANs are even greater than for VLANs because wide area connections can be share and made over low-cost public Internet circuits saving a lot of money and providing greater capacity than leased point-to-point circuits.

A common example would be to have two different internet service providers connected to a Meraki MX appliance and configure the MX to send voice traffic on the link with the lowest latency, jitter and packet loss. You will be able to monitor the links in the dashboard and see when the MX has made decisions dynamically to route voice traffic over either link. The links may also be site-to-site VPN links to other branches or locations. Many organizations are choosing to move away from expensive dedicated WAN links to SD-WAN since the performance can be similar and the price less.

Here is simple diagram depicting two MX appliances each with two internet connections and site to site VPN:

So what is SD-WAN exactly? Much like the "cloud", it can have different meanings to different people. Broadly speaking, SD-WAN is a generic term for a set of features that makes Internet connections a lot more useful. Let's take a real-life example of how SD-WAN could be used to solve a business problem. Let's say you have a VoIP phone system and all of your calls are made over the Internet. You also have one Internet connection which is great for browsing the web and checking email, maybe accessing an online service or two. Well what happens if you are on a phone call about to close a big sale, and the Internet goes down? Well the call gets dropped and so do you. SD-WAN could be used to ensure that your call continues even if your Internet goes down. Voodoo magic? Not really, but kinda.

The way SD-WAN allows your call to keep going is that it uses a second internet connection and simply reroutes your call using the other connection instead. It does this by intelligently monitoring both connections in real time and deciding which one is the best connection to use at any given point in time. You stay on the call and win the deal. Good job!

This is just one example of how SD-WAN is being used in businesses today. On a more conceptual level, SD-WAN takes the idea of using one or more Internet connections and applying some kind of software logic to them. Meraki does this by taking two Internet connections and grouping them together to form a new virtual connection. This is helpful because the new virtual connection is now independent of the underlying Internet providers. Just the way virtualization (think Hyper-V or VMWare) makes the underlying hardware irrelevant to the virtual machines, so SD-WAN does for Internet connections. Ultimately, as with many modern technologies, the actual magic of what happens and how this works is transparent to the end user. All they know and care about is that it works. As a technology professional, you can now deliver that to them as a powerful solution. Go, you!

Think of a fish tank .... old fish tanks were simple, you dump the water, change it out for new and go on.

New one's, you have filters, flow control, inject air and clean.

SD WAN is to networks, what modern technology is to fish tanks, the better it is, the more visibility you have and easier it is for traffic to flow. You can scale up to a larger platform if needed, but you get the options for better visibility, extra security, filtered traffic and much more. Would you rather have a fish tank with SD WAN or without?

"SD-WAN is a new technology that help you when all of your family is downloading stuffs and you can't even watch a Youtube video properly. Instead of having a very bad quality, you can use different ways to access internet, and everyone is happy. And all of that with only 1 device !"

Think of it like a 4x4 system in a vehicle back in the today compared to now where we have auto AWD systems.

Think of each wheel as a different ISP.

Your driving in your vehicle (company) and you hit some bad terrain (ISP issues/black ice). Back in the day you had to stop the vehicle (WAN goes down, network stops), put it in neutral and change it to 4x4 mode (physically moving Ethernet cable from one router to another or waiting for some sort of fail over timer to kick in), and then speed back up.

Nowadays, your vehicle has auto/dynamic 4x4 (AWD / SD-WAN) so you don't have to do anything. It just starts providing power to the wheels (ISPs) that need it to make sure your vehicle (company) is still moving forward. The vehicle (company) never slows down. =)

Software Defined Wide Area Network is best described as the modern aged, secure connection to the rest of the world with flexible manageability. It is the new and improved connection to the internet.

You are no longer limited to having a piece of hardware for each and every different function you may require for security, manageability, and ease of use on a network and instead can replace these hardware pieces with a very easy to use "Software" on one device.

It will support multiple connection types such as your ISP's connection at home bringing you access to the web combined with another type such as the LTE connection in your mobile phone. This allows fail-over or load balancing in case one happens to go down, the network will still be able to remain up with no interruption to users.

The ability to to select the most optimal paths for the data to be routed is in place so there will be virtually no lag time.

A modern, yet simple User Interface is in place to control all devices on the network is provided. Think Apple's simplistic UI for the iPhone; it's easy to pick up and get around without a long list of instructions (even your grandma can control with little to no assistance!)

It has the ability to act as a firewall, VPN, etc. (These help keep the bad guys out while securely letting the good guys in. You can connect up to your work or school computer from virtually anywhere using secured VPN.

The bell rings loudly at the firehouse and the fire crew jumps into action. They quickly dress and hop aboard their shiny red fire truck and pull out of the station. They've got just minutes and need to be on the scene quickly. Luckily, the driver of fire truck knows how to get the crew to any location in the fastest way possible—her mind is filled with detailed maps and knowledge about the layout of the town—but more importantly, she has procedure rules to follow based on the density and speed of the traffic she might encounter. You see, the fire crew—any fire crew—is extremely sensitive to latency: any delays or a high-number of jittery-drivers in front of them could spell disaster for saving people from the blazing building across town.

Our driver knows the established policies based on conditions seen along her route. Should there be a slow-down or even bumper-to-bumper traffic on the freeway, then she needs to drive on the shoulder of the road. What if the projected route is under construction and there's no ability to drive on the shoulder because concrete barricades have narrowed the lanes? She has a policy or a procedure for that, too. She can drive an alternative route (such as back-roads or feeder roads) or even drive on the wrong side of the street to meet her timeliness objectives.

Meraki SDWAN delivers all of this giving a confidently connected and protected network, delivering your business applications and data, prioritized and optimized, where they are needed.

Remember when the CD was a thing. you had to spend time storing, categorizing, cleaning, insuring.

To play your music you need to decide quality sound versus portability with it skipping tracks on the move. You need to load your ten stack CD to get and extended playlist. All time consuming, not very flexible, and not necessarily delivering the desired experience.

Well Meraki SDWAN for networks is like the Spotify for music. It's Simple to use, you can Control many devices from the one dashboard, you have Visibility of you playlists and Agility to select and queue as many songs as you like. With a huge Scale of songs and great sound Performance all from your Secure login.

Imagine instead of going to different stores and trying to find what you want. You'd have to go to multiple places and try to find the right route to get what you need. SD-WAN makes it so that you go to a central location with a travel guide of where you need to go or the right paths to get there.

SD-WAN is a technology that can be acquired to simplify the management and administration of all the resources of a network, that is, the IT administrator will have the facility of being able to have active notifications through a single interface offering a friendly environment in the administration and management of operability without impacting the implementation costs, that is, SD-WAN can offer low costs and the cost-benefit ratio will have a great impact on the clients' economy